This invention relates generally to storage systems associated with computer systems and more particularly to providing a method and apparatus for dynamically reconfiguring the logical volumes of a data storage system. That is, the invention provides a storage system which allows for re-partitioning of the addressable blocks of main storage space, while a storage system is on-line, with no downtime.
Computer systems generally include a central processing unit, a memory system, and a data storage system. Some modem computer systems which include both mainframe and open system platforms, may use a sophisticated storage system to simultaneously provide storage for different data formats (e.g. CKD and FBA). An enterprise data storage system (EDSS), such as the Symmetrix ESP by EMC Corp., may be used to provide such storage needs. An EDSS is a versatile data storage system having the connectivity and functionality to simultaneously provide storage services to types of host computers (e.g. mainframes and open system hosts). A large number of main, physical storage devices (e.g. an array of disk devices) may be used by an EDSS to provide data storage for several hosts. The EDSS storage system is typically connected to the associated host computers via dedicated cabling or a network. Such a model allows for the sharing of centralized data among many users and also allows a single point of maintenance for the storage functions associated with the many computer systems.
Today's physical storage devices may include disk drives, tape drives, and optical drives. A physical storage device generally corresponds to a physical volume. The physical volumes are generally associated with logical volumes so that the storage devices can be accessed in a convenient manner by the attached host computers. A storage system's logical to physical relationship may be established by mapping the physical volumes to logical devices which accommodate storage needs of the applications or operating systems associated with the host computers attached to the storage system. The logical device sizes and configurations are limited by a storage system physical constraints as well as the attached host types (e.g. mainframe and open system type computers). Once logical volumes are established, the attached host computers can access the storage space using logical addresses and control signals. The logical volumes, therefore, and not the physical volumes, are seen as storage space by the attached hosts.
In order to configure logical volumes, present prior art storage systems require a system administrator, using a Logical Volume Manager software package, to configures the logical volumes while the storage system is off-line. Once the logical volumes are configured, an attached host may then begin communications with the new logical volumes However, in order to recognize the new logical volume configuration, a host and the associated storage system may need to be re-initialized or rebooted. After the host completes the boot procedure, the host can then scan the associated buses (of the storage system) and determine the logical volumes that are dedicated to its storage needs.
During the life of a storage system, it often becomes necessary to increase the physical storage space or reassign certain storage resources to different hosts. This modification may be done to accommodate more hosts, add user accounts, add or reallocate volumes, modify assignments of hosts to storage resource, or change emulation modes. Also, the storage resources may simply be reallocated among the active hosts in order to provide a different configuration with to achieve different security features, greater performance, or increased reliability. These modifications require a reconfiguration of the logical volumes so that the new or altered physical volumes can be mapped to logical volumes and used by the attached hosts. Prior art storage systems must be off-line for logical volume reconfigurations. That is, all storage devices within the storage system being reconfigured are not accessible by any host during the logical volume reconfiguration. Shutting down a storage system, especially an EDSS, for a logical volume reconfiguration is usually complex, cumbersome, and inefficient. It may even be economically impossible since many business environments require that the disk devices of a storage system be available twenty-four hours a day, seven days a week. It would be advantageous therefore to provide a dependable procedure for reconfiguring the logical volumes of a storage system, while simultaneously allowing the hosts to actively access the logical volumes of the original configuration so as not to disturb any active applications.